ABSTRACT We present a discovery and therapeutics development program to establish alternative splicing as a therapeutic target of Myc-driven prostate cancer. The Myc-family of proto- oncogenes, including c-Myc, N-Myc, and L-Myc, play a central role in the pathogenesis of this and many other cancers. Yet therapies inhibiting Myc action have yet to reach the clinic. As transcription factors, Myc proteins are difficult to target with either small molecules or immunotherapeutics. Indirect strategies that target downstream effectors of the Myc expression program may prove more successful. Our strategy is to target the splicing factors and alternatively spliced isoforms that the multiple Myc paralogs rely on to drive prostate cancer. Myc has been recently shown to control alternative splicing patterns that are crucial to Myc-driven tumor growth. We hypothesize that these tumors rely on specific splicing regulatory proteins that can be identified and potentially targeted with small molecules. In parallel, we hypothesize that Myc-driven alternative splicing will create cancer-specific protein isoforms suitable for immunotherapeutics development. Given the ubiquity of Myc deregulation in human cancer, we anticipate that our results will be of broad relevance to the cancer research community. We have assembled a team of investigators at UCLA with extensive experience in bioinformatics (Yi Xing), alternative splicing (Douglas Black), and cancer cell biology and immunology (Owen Witte). Our proposal integrates the analyses of cancer genomic data with focused experimental research using unique Myc-transformed human prostate materials. We will gather data on Myc-dependent alternative splicing in normal prostate tissues and primary cancers from large datasets (TCGA, GTEx) as well as datasets representing advanced disease states. Total proteomics analysis will be conducted on our transformed materials to confirm protein expression of candidate isoforms. We will employ a high-throughput screening platform developed in one of our labs to identify genetic or chemical modulators of Myc-dependent splicing events. Candidate cell surface isoforms selected for immunotherapeutics development will carry cancer- specific exon-exon junctions suitable for antibody development with phage display libraries. High-affinity, high- specificity antibodies will be built into CAR T-cells for further development